Such an anesthetic dispenser is disclosed, for example, in EP 0 469 797 B1.
In case of the anesthetic desflurane, which is known per se, the anesthetic tank with the desflurane reservoir to be dispensed is heated in order to achieve a controlled release of the anesthetic in the form of a saturated vapor flow. This occurs due to the low boiling point of desflurane. Mixed gas flowing in from the anesthesia apparatus is sent in the anesthetic dispenser through a fixed resistance, namely, a bypass resistance or bypass gap. The pressure dropping over this fixed resistance is compared with a pressure that drops over a variable settable resistance, namely, a dispensing gap, and through which saturated desflurane vapor flows. By means of the dispensing valve designed as a proportional valve, a controller sets the saturated desflurane vapor flow such that the pressures before the fixed resistance and after the variably settable resistance are equal. As a result, the dispensing of desflurane is set such that the quantity of desflurane being dispensed and consequently the concentration present in the fresh gas released depend only on the position of the handwheel setting the dispensing gap and not on the mixed gas flow flowing in. The controller as well as all safety and test functions are embodied in an electronically programmed manner in this case.
A safety valve (shut-off valve) is located between the heated anesthetic tank and the dispensing valve. Both the dispensing valve and the safety valve must close reliably for the safe use of the anesthetic dispenser described to make sure that in case of a valve defect, the corresponding other valve can reliably interrupt the saturated vapor flow and the patient is thus prevented from being exposed to danger, for example, due to the overdosage of saturated vapor.
If the safety valve had a leak due to a defect, saturated vapor would continue to flow in the direction of the patient in an uncontrolled manner, which could lead to danger for the patient in the extreme case. The object arising from this is to provide a process for monitoring the valves of an anesthetic dispenser with two valves connected in series, which can be carried out safely and in a simple manner.